/**
 * Copyright (c) 2024 Hunan OpenValley Digital Industry Development Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "GPUImageGrayscaleFilter.h"

const std::string GPUImageGrayscaleFilter::GRAYSCALE_FRAGMENT_SHADER = R"(
    #extension GL_OES_EGL_image_external : require
    precision highp float;

    varying vec2 textureCoordinate;

    uniform samplerExternalOES inputImageTexture;

    const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);

    void main()
    {
        lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
        float luminance = dot(textureColor.rgb, W);

        gl_FragColor = vec4(vec3(luminance), textureColor.a);
    }
)";
